Data caching is a significant factor in providing rapid content retrieval while avoiding the overloading of content servers with content access requests. A problem with caching is that caches have many variables that need to be considered to provide a desired outcome.
One consideration is whether to use a FIFO (first-in, first out) cache or a LRU (least recently used) cache. Another consideration is the cache size, as in general, the more data that can be cached, the greater the cache hit rate. However cache size is generally limited to a percentage of available memory, which is a valuable resource. Also, the longer the retention time of cached data the greater the hit rate, but serving stale data, at least not too stale, is not acceptable in most scenarios. Thus, the type and amount of data to be cached are considerations.